The need for a toner suitable for high-speed printing, particularly toner capable of improving image quality and preventing hot offset is increasing in the printing industry. “Hot offset” is a phenomenon whereby melted toner on a printing paper adheres to a fixing device after passing through the fixing device when an amount of toner exceeding the amount required to be fixed on the printing paper is excessively melted when the toner is heated while passing through the fixing device.
Thus, toner requires resistance to hot offset.
In particular, toner used for full color printing needs to sufficiently realize and reproduce a desired color by a fixing process using heating and pressurizing without reducing clearness of images. Thus, the toner used for full color printing is required to include a low molecular weight binder resin that melts instantly. However, since the aggregating ability of the instantly melting low molecular weight binder resin decreases during the fixing process using heating and pressurizing, hot offset may easily occur.
In this regard, toner having a predetermined storage modulus and loss modulus at a specific temperature range has been reported.
Japanese Patent Publication No. 1996-054750 discloses a toner having a predetermined storage modulus at 170° C., and Japanese Patent Publication No. 1999-084716 discloses a toner having a predetermined loss modulus at 180° C. However, these toners have the confrontation of fixing properties at low temperature and hot offset properties, and poor heat-resistant storage properties due to low viscosity.
Japanese Patent Publication No. 1994-059504 discloses a toner having a predetermined storage modulus at a temperature ranging from 70 to 120° C., and Japanese Patent Publication No. 1999-007151 discloses a predetermined loss modulus at a temperature ranging from 130 to 180° C. However, these toners have poor heat-resistant storage properties, resolution, charging properties, and developing properties.
Japanese Patent Nos. 1993-249735, 1995-234542, 1995-295298, 1996-278662, and 1998-171156 disclose toners having a desired storage modulus, loss modulus, or loss tangent that is a ratio of a loss modulus to a storage modulus in a predetermined temperature range. However, storage properties, preservation properties, glossiness of those toners are not sufficient for a color toner.
Thus, there is still a need to develop a toner having excellent charging properties, developing properties, glossiness, fixing properties, and resistance to hot offset.